Usually, combination locks consist of a plurality of wheels on the peripheries of which digits are engraved, which wheels are mounted on a single shaft by means of bushings meshing with said wheels by means of reciprocal teeth or a similar solution, which bushings have a flat undercut such that when said undercuts are aligned and the correct, pre-established combination is set, it is possible for a part to be moved and hence the lock or the like to be opened.
This known arrangement of digit-bearing wheels meshing with bushings enables the radial position of the wheels to be changed with respect to the bushings if the wheels and bushings are disengaged, enabling the opening combination to be changed according to the wish of each user.
Specifically, in combination locks, despite the small size of these elements, this disengagement or combination-change mechanism consisted of displacement of the shaft on which the wheels and bushings rode, a relationship existing between these bushings and said shaft which enabled their respective rotation and made them integral in this axial entrainment for disengagement against some elastic means which maintained the operating position of the assembly.
This solution has a number of disadvantages such as the space and the special arrangements the padlock casing must present to permit displacement of the shaft, which negatively affects both the size of the padlock and its manufacture and operation. On the other hand, since axial solidarity is required between the bushings and the shaft, the latter must have some shape or [have] some element establishing this relationship which must be achieved by a mechanical operation implying a further manufacturing step with a consequent increase in the cost of the lock.